1. Field of the Invention
The present invention relates to a seal structure between a cylinder head and a head cover in an engine, including a seal member interposed between the cylinder head and the head cover, the cylinder head having a slant at least at an intermediate portion of its upper end face to which a valve-operating cam chamber opens, the head cover being coupled the upper end face of the cylinder head by a bolt to close the valve-operating cam chamber.
2. Description of the Related Art
In a conventional engine, joint surfaces of a cylinder head and a head cover are formed in one plane, and a seal member such as an O-ring, a gasket or the like, is interposed between the joint surfaces to provide the sealing between the cylinder head and the head cover. In such a seal structure, it is necessary for ensuring a normal seal function to couple the cylinder head and the head cover to each other by a large number of parallel bolts, to equalize the interference of the seal member at various portions.
If the upper end face of the cylinder head is formed according to the shape of a mechanism within a valve-operating chamber in order to make the engine more compact, the upper end face may be a three-dimensional face having a slant at its intermediate portion. In such a case, it is difficult to equalize the interference of the seal member at various portions, even if a large number of parallel bolts are used as in the prior art. Moreover, the use of the large number of bolts does not permit a reduction in cost.
Accordingly, it is an object of the present invention to provide a seal structure between the cylinder head and the head cover in the engine, wherein an interference uniform at the various portions of the seal member can be provided irrespective of the number of bolts used, and the seal member can always exhibit a good seal function.
To achieve the above object, according to a first aspect and feature of the present invention, there is provided a seal structure between a cylinder head and a head cover in an engine, comprising a seal member interposed between said cylinder head and said head cover, said cylinder head having a slant at least at an intermediate portion of an upper end face of the cylinder head to which face a valve-operating cam chamber opens, said bead cover being coupled to the upper end face of said cylinder head by a bolt to close said valve-operating cam chamber, wherein the head cover has a fit wall portion formed thereon and fitted to an inner peripheral surface of the valve-operating cam chamber, and the seal member is mounted in a seal groove provided in an outer peripheral surface of the fit wall portion to come into close contact with an inner peripheral surface of the cylinder head.
With the above arrangement, an interference uniform at the various portions of the seal member can be provided irrespective of the number of bolts used and an axial force, thereby ensuring a good sealed state between the cylinder head and the head cover. Moreover, bolts for securing a flange portion of the head cover to the cylinder head do not affect in the interference of the seal member and merely performs the securing of the head cover to the cylinder head. Therefore, it is possible to reduce the number of the bolts required, thereby reducing the cost.
According to a second aspect and feature of the present invention, in addition to the first feature, the upper end face of the cylinder head comprises a pair of flat face portions which are parallel to each other at different height levels, and a slant connecting the flat face portions to each other, and the head cover is formed with a flange portion abutting against the upper end face, the flange portion being coupled to the cylinder head at locations corresponding to the flat face portions by bolts.
With the above arrangement, the head cover can be secured simply and reliably by a small number of bolts.